Process of heating olefin feed to dehydrogenation process



April 20, 1965 G. P. BAUMANN PROCESS OF HEATING OLEFINFEED TODEHYDROGENATION PROCESS Filed May 27, 1960 WATER LIQUID BUTENES GeorgeP. Boumcmn Inventor Pcnenf Attorney United States Patent 3,170,709PROCESS OF HEA'HNG @LEIFW FREE) TO DEHYDROGENATION PROUESS George I.Baumann, Sparta, NHL assignor to Esso Research and Engineering Company,a corporation of Delaware Filed May 27, 1900, Ser. No. 32,3115 6 Claims.(Cl. 200-680) This invention relates to a novel and improved process andapparatus for vaporizing and heating C to C olefins to high temperaturesin the range of 600 to 1100 F. More particularly this invention relatesto vaporizing these feed stocks by contacting them countercurrently withsteam in a distillation tower. Thus, according to this invention steamis condensed and provides a liquid wash on the stripper trays whichwashes any deposits formed off the trays. Yet more particularly, in apreferred embodiment, this invention relates to vaporizing and heating C-C olefinic feed stocks in such a tower pnlor to their being supplied tothe dehydrogenation furnace and reactors where these feed stocks areconverted to dioleiins. Most particularly, in a preferred embodimentthis invention relates to supplying a C -C olefin-containing liquidstream to the top of a distillation column, supplying at least asufiicient amount of steam to a lower section of said column to obtainsubstantially complete vaporization of the olefin stream, removingvaporized olefins overhead from the top of said column, the saidvaporized olefins being at a temperature in the range of 100 to 300 F.,and removing condensed water from the bottom of the column. Theresultant C -C olefin-containing stream comprising 5 to 15 volumepercent of C -C hydrocarbons intermixed with 85 to 95 volume percent ofsteam is then heated to 1000 to 1350 F. and passed over a calcium nickelphosphate catalyst to effect the conversion of said C to C olefins tothe corresponding diolefins.

According to the present invention it has now been discovered that thevaporization and heating of C -C olefinic feeds can be much moreefficiently and cheaply obtained with less formation of undesirabledegradation byproducts by vaporizing the feeds with steam (preferablycountercurrently in a tower). Prior to the present the vaporization ofstreams of this type in conventional heat exchangers or furnaces hasresulted in excessive fouling of the equipment. This fouling requiredeither frequent shutdowns for cleaning or preferably the design of spareequipment to allow cleaning of one of the units while the other was onstream. According to the present invention an extremely efficientvaporization of these olefin streams is obtained at any pressure withessentially no fouling and less degradation of the feed stream.

For economy purposes it is preferable to supply substantially saturatedsteam to the vaporizer. Thus, the latent heat evolved upon condensationof the steam supplies the majority of the heat required for vaporizationof the hydrocarbon stream. However, it is of course contemplated that ifdesired superheated steam may be utilized.

This invention will beparticularly advantageously applied indehydrogenation processes for converting C -C olefins to diolefins. Inthese processes fouling of conventional heat exchangers or furnaces usedfor preheating and vaporizing the feed prior to its being supplied tothe main dehydrogenation furnace have been particularly se- Vere. Thetemperatures and composition of the feed streams to be supplied to thevaporizer in these processes along with the general reaction conditionsare described below.

hydrogenation of n-butenes to butadiene.

Butene dehydrogenation to bumdiene Range Preferred Specific FeedComposition:

n-Butylene, Wt. Percent 20-100 40-85 75. 0 Isobutylenc, Wt. Percent.0-30 0-3 1. 5 Butanes, Wt. Percent 0-60 10-60 24. 5 Pressure inVaporizer, p.s.1.a 20-300 -140 Steam/f; Feed in Effluent Supplied toFurnace 0.1-1.0 0. 1-0. 5 0; 23 Furance Inlet Temperature, F 100-400-250 200 Range Specific Reaction Conditions:

Space Velocity of n64", v./v./hr. 75-170 120 Space Velocity of Steam,v./v./hr. 1, 400-10, 000 2, 300 Reactor Inlet Temperature, F.-. 000-1,350 1, Reactor Outlet Pressure, p.s.i.a 15-30 20 n-Butylene Conversion,percent per pass 30-75 40 Selectivity to Butadiene, percent 75-95 85Catalyst:

1 V./v./hr.=volume of gas at S.I.P./volume catalyst/boon Isopentenedehydrogenation to isoprene Feed Composition Range Pericrred SpecificZ-mcthyl Butcnes, Wt. Percent 20400 40-85 75.0 Other 0 Olcfins, Wt.Percent- 0-30 0-3 1. 5 C Paratfins, Wt. Percent 0-60 10-60 24. 5

Same vaporizer pressures. f Same dehydrogenation finance teedtemperatures and steam proporions.

Same reaction conditions as in dehydrogenation of butenes.

Dehydrogenation of 2,3-dimethyl butene to 2,3-dimethyl butadi ne Samevaporizer pressures. noSgismc dehydrogenation furnace feed temperaturesand steam propor- Same reaction conditions as in dehydrogenation ofbutcnes.

The present invention will be more clearly understood from aconsideration of a particular process for the de- In this process thebutene-butane feed mixture is vaporized and heated to about 200 F. priorto its being passed to the cracking furnace. In the prior art processesvaporization of thisfeecl stream was obtained in commercial heatexchange equipment (tube and shell exchangers) with low level heat. Incommercial operations using this process the vaporization of the buteneshas resulted in excessive fouling so that ordinarily a 100% spare bundleof tubes has been necessary to allow cleaning without disrupting theoperation. This spare bundle and piping involved, of course adds to thecapital investment and the frequent cleaning required increasesoperating costs.

According to the present invention referring to the figure, the liquidbutene-butane feed stream is. supplied after some preheating if desiredthrough line I to tower 2, containing a series of bubble plates, 3, d,5, and 6 with associated downcomers. The feed stream is supplied in apreferred embodiment above plate 6 and steam is supplied through line 8to the tower below plate 3. The liquid butene-butane stream descendingthrough the tower is countercurrently contacted with the steam, thusobtaining essentially complete vaporization of the liquid butene-butanestream overhead. The vaporized butenebutane stream is taken from the topof the tower through line 9 and condensed water is taken from the bottomof the tower through line 10. It should be noted that the condensationof the steam on each plate continuously provides the heat to vaporizethe butenes and also provides a liquid wash on the stripper trays whichWashes deposits off the trays. It is, of course, contemplated that othertypes of plates in the tower rather than bubble plates may be used andthat also less desirably a packed column rather than a plate column maybe used.

An additional advantage of this process results from the periodic needto remove feed for emergency repairs or accidental loss of feed to thebutene dehydrogenation plant due to maloperation of catalyst reactorequipment such as automatic cycle timer and motor operated valves.During this period extra steam over that required for vaporization ofbutenes is required to adjust the furnace tube mass velocity so that theamount of hydrocarbon cracking occurring in the butene furnace isminimized. This addition of steam may be extremely advantageouslysupplied from the present type vaporizer since when hydrocarbon feed iswithdrawn an automatic increase in steam evolved occurs due to thereduction in the steam condensed by the hydrocarbon. It should be notedthat without the availability of additional steam the cracking furnacemust be quickly shut down whenever a loss of feed occurs. Thus, withouta feed stream the furnace will quickly burn out with failure of thefurnace tubes and/or brickwork and structural steel.

It is estimated that the inherently improved operations resulting fromthis invention will provide large savings. Thus, for example investmentsavings alone have been estimated to be in the order of $20,000 for asmall unit producing 35 tons of butadiene per day.

The foregoing description contains a limited number of embodiments ofthe present invention. It will be understood that this invention is notlimited thereto since numerous variations are possible without departingfrom the scope of the following claims.

What is claimed is:

1. An improved process for vaporizing and heating a liquid hydrocarbonfeed stream containing at least 20 Wt. percent of C -C olefins, themajor proportion of the remainder of said feed stream consisting of C -Chydrocarbons which comprises supplying said feed stream to the top of adistillation column and supplying at least a suflicient amount of steamto a lower section of said column to obtain substantially completevaporization of C -C the olefin content of said feed stream and steamessentially no fouling of the heat exchange surfaces of thedehydrogenation furnace and less degradation of the feed stream.

2. The process of claim 1 wherein said steam is saturated steam.

3. In a process for dehydrogcnating a C -C olefin containing streamwherein said olefin stream is passed with to volumn percent of steambased on the total stream supplied at temperatures of 1000 to 1350" F.over a calcium nickel phosphate catalyst, the improvement whichcomprises vaporizing and heating a liquid hydrocarbon feed streamcontaining at least 20 wt. percent of C -C olefins, the major proportionof the remainder of said feed stream consisting of C -C hydrocarbonsprior to its being supplied to the dehydrogenation reactor by contactingsaid feed stream in a distillation column with at least that amount ofsteam to obtain substantially complete vaporization and heating of the C-C olefin content of said feed stream removing steam and vaporizedolefins overhead from the top of said column and condensed water fromthe bottom of the column, charging the vaporized olefins and steam to adehydrogenation furnace and heating the same to temperatures of about1000l350 F. whereby said olefin feed is heated to active dehydrogenationtemperatures with essentially no fouling of the heat exchange surfacesof the dehydrogenation furnace and less degradation of the feed stream.

4. The process of claim 3 in which the olefin stream is a C streamcontaining 20 to wt. percent n-butylene, 030 wt. percent isobutylene and060 wt. percent butanes.

5. The process of claim 3 in which the olefin stream is a C streamcontaining 20100 wt. percent 2-methyl butenes, 0-30 wt. percent other Colefins and 0-60 wt. percent C parafins.

6. The process of claim 3 in which the olefin stream is a C streamcontaining 20 100 wt. percent 2,3-dimethyl butenes, 0-30 wt. percentother C olefins and 0-60 wt. percent C parafiins.

References Cited by the Examiner UNITED STATES PATENTS 2,297,004 9/42Lee 202-46 2,367,623 1/45 Schulze et al 260--680 2,411,808 11/46 Rupp eta1 260--677 2,459,449 1/ 49 Oliver et al 260-680 2,509,900 5/50 Wormith260680 2,733,285 1/56 Hammer 260683.15 2,918,508 12/59 Coopersmith eta1. 260683.l5 2,957,928 10/60 Cann 260-680 FOREIGN PATENTS 591,209 1/60Canada.

OTHER REFERENCES Faradays Encyclopedia of Hydrocarbon Compounds, by J.E. Faraday and A. S. Freeb'orn, page 060160801 (1960, received July 18,1961) pages 060550091 and 060930091 (1953, received January 26, 1954);volume 2a, Chemindex Limited, London, 1960.

ALPHONSO D. SULLIVAN, Primary Examiner.

MILTON STERMAN, Examiner.

1. AN IMPROVED PROCESS FOR VAPORIZING AND HEATING A LIQUID HYDROCARBONFEED STREAM CONTAINING AT LEAST 20 WT. PERCENT OF C4-C6 OLEFINS, THEMAJOR PROPORTION OF THE REMAINDER OF SAID FEED STREAM CONSISTING OFC3-C6 HYDROCARBONS WHICH COMPRISES SUPPLYING SAID FEED STREAM TO THE TOPOF A DISTILLATION COLUMN AND SUPPLYING AT LEAST A SUFFICIENT AMOUNT OFSTEAM TO A LOWER SECTION OF SAID COLUMN TO OBTAIN SUBSTANTIALLY COMPLETEVAPORIZATION OF C4-C6 THE OLEFIN CONTENT OF SAID FEED STREAM AND STEAMAND VAPORIZED OLEFINS OVERHEAD FROM THE TOP OF SAID COLUMN AND CONDENSEDWATER FROM THE BOTTOM OF THE COLUMN, AND CHARGING VAPORIZED OLEFINS ANDSTEAM TO A DEHYDROGENATION FURNACE AND HEATING THE SAME TO TEMPERATURESOF ABOUT 1000-1350*F. WHEREBY SAID OLEFIN FEED IS HEATED TO ACTIVEDEHYDROGENATION TEMPERATURES WITH ESSENTIALLY NO FOULING OF THE HEATEXCHANGE SURFACES OF THE DEHYDROGENATION FURNACE AND LESS DEGRADATION OFTHE FEED STREAM.